Pockels Langmuir monolayer

Molecule 11 forms amphiphilic Pockels-Langmuir monolayers at the air-water interface, with a collapse pressure of 34 mN m and collapse areas of 50 A at 20 °C these monolayers transfer on the upstroke only, with transfer ratios around 100% onto hydrophilic glass, quartz, or aluminum,or onto fresh hydrophilic Au, but transfer poorly on the downstroke onto graphite, with a transfer ratio of only abont 50%. The LB monolayer thickness of 11 was 23-25 A by X-ray diffraction, spectroscopic ellip-sometry, surface plasmon resonance, and XPS. With... 

Figure 5.3 Film balances a. Langmuir trough having a movable barrier and a Wilhelmy tensiometer to measure the spreading pressure, n, for water insoluble monolayers, b. PLAWM (Pockels, Langmuir, Adam, Wilson and McBain) trough used for partially water-soluble monolayers, where a flexible membrane, which is fixed to the barrier, separates the surfactant solution and pure water departments to prevent the passage of dissolved surfactant molecules into the pure water department beneath the barrier.

Film Balance A shallow trough that is filled with a liquid on top of which is placed material that may form a monolayer. The surface area available can be adjusted by movable barriers, and any surface pressure thus created can be measured by means of a float. Also called Langmuir Film Balance, Langmuir Trough, and Pockels—Langmuir—Adam—Wilson—McBain Trough or PLAWM Trough. 

For many years, the main experimental tool for these studies was the film balance (see Figure 4.19). Various workers, including Pockels, Langmuir, and Adam, made major contributions to its development (see Gaines, 1966). A small, known quantity of the surfactant to be studied is dissolved in a volatile solvent and deposited carefully by pipette on the surface of a pool of water. The solvent is chosen so that it spreads rapidly over the water and then evaporates, leaving the surfactant uniformly distributed as a monomolecular layer (or monolayer) in the region between the two barriers. One of the barriers is movable, so that the area occupied by the surfactant film can be varied. A torsion balance is provided to measure the surface pressure (i.e., the difference between the surface tension of pure water and that of the film-covered surface). More commonly in modem instruments, a Wilhelmy plate is used to measure surface tension in the film region. 

The variant of 11 with an undecyl tail followed by a thioacetyl termination ( Cll thioacetyl ) gave disappointing results the Pockels-Langmuir film collapsed at relatively low surface pressures, compared to 11, and yielded disordered LB monolayers, with competition between strong physisorption by the dicyanomethanide end of the molecule and Au-to-thiolate chemisorption. The monolayer rectified in either direction, depending on where in the LB monolayer, that is, on which molecule ( right side up or upside down ) the STM tip was probing. ... 

As shown by Pockels, Langmuir [24 - 26] and others, amphiphilic molecules, including lipids, can be stabilised as monomolecular layers at the air-water interface. Also, some proteins can self-assemble - on their own or with lipids - at the air-water interface to form monolayers, e.g., lipase [27], bacterial surface-layer proteins [28, 29], or trans-membrane proteins such as bacteriorhodopsin [30], Transfer of monomolecular layers to solid support by the Langmuir-... 

The first to perform wave-damping measurements in a kind of Langmuir trough, i.e., under different compression status of the monolayer, was Agnes Pockels (1891). Ironically, she described for the first time an apparatus that was... 

Surface studies of insoluble monolayers of all the common unconjugated bile acids, including the unsubstituted cholanoic acid, have been carried out by a number of workers and thoroughly reviewed [5]. Being insoluble non-swelling amphiphiles with limited aqueous solubility, their surface pressure-area (v-A) isotherms can be measured satisfactorily with a Langmuir-Pockels surface balance on an aqueous subphase containing 3-6 M NaCl to salt out polar functions and at sufficient acidic pH (1-3) to prevent ionization [5,6). 

As part of his work on surfaces, Langmuir studied monolayer films on water surfaces, with techniques pioneered by a chemist who started her studies in greasy dishwater Agnes Pockels. 

The scientific approach of interfacial phenomena started in the second half of the eighteenth century with B. Franklin s reports in 1765 on the amount of oil needed to cover the surface of Clapham Pond in England. Later, in the nineteenth century. Lord Rayleigh pursued these experiments and A. Pockels and I. Langmuir did the first quantitative studies on the properties of monolayers of surface-active substances at liquid/air interfaces. 

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